This invention relates to a rotary scanner flaw detection system for the detection of flaws on a moving sheet or web of material, and more particularly to such a system having a record medium memory means driven in synchronism with the scanner which is utilized for dividing the material electrically into discrete segments or strips for providing a means of sorting or routing flaw information from the material in order to determine readily where the flaws occur on the material being examined.
The present invention has application to the type of flaw detection system shown and described in U.S. Pat. No. 3,781,531 issued Dec. 25, 1973, and patent application Ser. No. 449,247, filed Mar. 8, 1974, now U.S. Pat. No. 3,900,265, and patent application Ser. No. 465,510 filed Apr. 30, 1974, now U.S. Pat. No. 3,920,970, all of which are assigned to the assignee of the present invention. In the aforesaid systems, flaws are detected on the surface of the material being examined by repetitively scanning a suitable source of radiation, such as a laser beam, across the surface of the material. The laser light is reflected, transmitted, or scattered from the material, depending on the characteristics of the material, which light is picked up by a receiver having a suitable detector such as a photomultiplier tube. At any instant of time during the scan, the photomultiplier output varies with the reflectivity, transmissivity, or scattering properties of the spot on the material upon which the laser beam is impinging, and deviations from normal variation provide a means for indicating the material flaws. For many applications it is desirable to readily determine on what portion of the sheet of material or web the flaws occur, the number of flaws occurring on a specific portion of the web, the repetition rate, etc. For example, the web of material may be plastic, paper, magnetic tape, etc., which is manufactured in a wider web than will ultimately be used, but is so manufactured for uniformity's sake and the savings in manufacturing cost in not having to make a plurality of webs in narrower widths. If flaw information is readily available which is related to the strips into which the web will be divided, then only the faulty strips or portions of the web need be discarded, thereby saving the areas of material which are unflawed. Furthermore, in the manufacturing process, if a flaw continues to exist along a certain strip or segment, it may be desirable to examine the manufacturing process pertaining to the area where the flaw continues to occur, to locate the portion of the manufacturing process which is faulty and producing flaws on the material.
One solution to the problem is to provide a multiplicity of systems which only scan predetermined portions of the web of moving material. This approach would be extremely expensive in the duplication of equipment as well as being unwieldy and difficult to implement, particularly if the web is to be divided into a large number of segments.
A more practical solution to the problem is disclosed in an application Ser. No. 475,189, filed May 31, 1974, entitled "Data Router for a Flaw Detection System," now U.S. Pat. No. 3,898,469, which is assigned to the assignee of the present invention. The laser scan inspection system of the aforesaid application segregates the extracted data in accordance with the section of the web in which a flaw occurs by the use of a digital selection system utilizing thumb-wheel switches. The thumb-wheel switches are utilized to establish markers or positions which identify the sections, strips, or lanes of the web on which flaw information is to be extracted. Since the scanning of a flat surface is not linear even when using a rotary scanner, the thumb-wheel switches are set utilizing some form of grating or marking which may be made directly on the material being examined, or on a separate material where the markers show up as signals on the detector output. The data routing system of the aforesaid application may be quite acceptable for the case where the web is to be divided into a relatively few strips or sections. A practical limit, however, exists, for example from one to approximately eight lanes, due to the amount of space required for the switches and their associated circuitry. Beyond this point a profusion of switches and components, along with the potential for error, makes this approach less practical. Since the primary function of the selector thumb-wheel switches is that of a mechanical memory, any other form of non-volatile, synchronized, and spatially correlated memory would represent a dramatic improvement in reducing the complexity of the equipment utilizing and providing a data-routing function.